There's no way we can just say X, Y or Z motor w/o some details.

What kind of motor are you even asking about? Electric, nitro, gas??? What kind of transmission, differential and gearing do you intend to use?

Personally, it doesn't sound to me like you are very familiar with rc either and I think that your $100 budget to build an rc from scratch is very unrealistic especially if you have to get electronics too.